Lhx2 selector activity specifies cortical identity and suppresses hippocampal organizer fate

The earliest step in creating the cerebral cortex is the specification of neuroepithelium to a cortical fate. Using mouse genetic mosaics and timed inactivations, we demonstrated that Lhx2 acts as a classic selector gene and essential intrinsic determinant of cortical identity. Lhx2 selector activity is restricted to an early critical period when stem cells comprise the cortical neuroepithelium, where it acts cell-autonomously to specify cortical identity and suppress alternative fates in a spatially dependent manner. Laterally, Lhx2 null cells adopt antihem identity, whereas medially they become cortical hem cells, which can induce and organize ectopic hippocampal fields. In addition to providing functional evidence for Lhx2 selector activity, these findings show that the cortical hem is a hippocampal organizer.

Dynamic spatiotemporal expression of LIM genes and cofactors in the embryonic and postnatal cerebral cortex

LIM-homeodomain (LIM-HD) genes encode a family of transcription factors known to be involved in development and patterning in several systems. Previously, we have shown that LIM-HD gene Lhx2 is required for the formation of a crucial boundary in the dorsal telencephalon (Bulchand et al. [2001] Mech Dev 100:165-175). To further explore the role of LIM-HD genes as well as the broader LIM gene family in dorsal telencephalic development, we examined the expression pattern of the members of this gene family and their cofactors in the developing mouse cerebral cortex. Transcription factor activity of the LIM-HD proteins requires the formation of a tetrameric complex consisting of two LIM-HD molecules linked by a dimer of cofactor (Clim) molecules. LIM-only (Lmo) proteins can interfere with this process by competing for the cofactors. LIM-HD protein function, thus, can be modulated by the presence of the appropriate Clim or Lmo molecules. At least 13 LIM-HD, 4 Lmo, and 2 Clim genes have been identified in the mouse. Several of these genes exhibit complex spatiotemporal patterns spanning different stages of cortical development, from embryonic to postnatal ages. Noteworthy features of the expression patterns include delineation of boundaries within the developing cortex, up- or down-regulation during formation of selected cortical layers, and a striking complementarity of expression of several members consistent with specific functions in cortical development. Significantly, in some cases, Lmo or Clim gene expression is robust where no LIM-HD gene expression is detectable. These results suggest multiple and distinct roles for LIM-HD, Lmo, and Clim genes in cortical development, and also support a LIM-HD-independent role for some Lmo and Clim members.

Two wound-inducible soybean cysteine proteinase inhibitors have greater insect digestive proteinase inhibitory activities than a constitutive homolog

Diverse functions for three soybean (Glycine max L. Merr.) cysteine proteinase inhibitors (CysPIs) are inferred from unique characteristics of differential regulation of gene expression and inhibitory activities against specific Cys proteinases. Based on northern blot analyses, we found that the expression in leaves of one soybean CysPI gene (L1) was constitutive and the other two (N2 and R1) were induced by wounding or methyl jasmonate treatment. Induction of N2 and R1 transcript levels in leaves occurred coincidentally with increased papain inhibitory activity. Analyses of kinetic data from bacterial recombinant CysPI proteins indicated that soybean CysPIs are noncompetitive inhibitors of papain. The inhibition constants against papain of the CysPIs encoded by the wound and methyl jasmonate-inducible genes (57 and 21 nM for N2 and R1, respectively) were 500 to 1000 times lower than the inhibition constant of L1 (19,000 nM). N2 and R1 had substantially greater inhibitory activities than L1 against gut cysteine proteinases of the third-instar larvae of western corn rootworm and Colorado potato beetle. Cysteine proteinases were the predominant digestive proteolytic enzymes in the guts of these insects at this developmental stage. N2 and R1 were more inhibitory than the epoxide trans-epoxysuccinyl-L-leucylamide-(4-guanidino)butane (E-64) against western corn rootworm gut proteinases (50% inhibition concentration = 50, 200, and 7000 nM for N2, R1, and E-64, respectively). However, N2 and R1 were less effective than E-64 against the gut proteinases of Colorado potato beetle. These results indicate that the wound-inducible soybean CysPIs, N2 and R1, function in host plant defense against insect predation, and that substantial variation in CysPI activity against insect digestive proteinases exists among plant CysPI proteins.

mTOR signaling regulates the morphology and migration of outer radial glia in developing human cortex

Outer radial glial (oRG) cells are a population of neural stem cells prevalent in the developing human cortex that contribute to its cellular diversity and evolutionary expansion. The mammalian Target of Rapamycin (mTOR) signaling pathway is active in human oRG cells. Mutations in mTOR pathway genes are linked to a variety of neurodevelopmental disorders and malformations of cortical development. We find that dysregulation of mTOR signaling specifically affects oRG cells, but not other progenitor types, by changing the actin cytoskeleton through the activity of the Rho-GTPase, CDC42. These effects change oRG cellular morphology, migration, and mitotic behavior, but do not affect proliferation or cell fate. Thus, mTOR signaling can regulate the architecture of the developing human cortex by maintaining the cytoskeletal organization of oRG cells and the radial glia scaffold. Our study provides insight into how mTOR dysregulation may contribute to neurodevelopmental disease.

Cortical Malformations: Lessons in Human Brain Development

Creating a functional cerebral cortex requires a series of complex and well-coordinated developmental steps. These steps have evolved across species with the emergence of cortical gyrification and coincided with more complex behaviors. The presence of diverse progenitor cells, a protracted timeline for neuronal migration and maturation, and diverse neuronal types are developmental features that have emerged in the gyrated cortex. These factors could explain how the human brain has expanded in size and complexity. However, their complex nature also renders new avenues of vulnerability by providing additional cell types that could contribute to disease and longer time windows that could impact the composition and organization of the cortical circuit. We aim to discuss the unique developmental steps observed in human corticogenesis and propose how disruption of these species-unique processes could lead to malformations of cortical development.

The anti-oxidant activity of turmeric (Curcuma longa)

The turmeric anti-oxidant protein (TAP) had been isolated from the aqueous extract of turmeric. The anti-oxidant principle was found to be a heat stable protein. Trypsin treatment abolished the anti-oxidant activity. The anti-oxidant principle had an absorbance maximum at 280 nm. After gel filtration, the protein showed a 2-fold increase in anti-oxidant activity and showed 2 bands in the SDS-PAGE with approximate molecular weight range of 24,000 Da. The protein showed a concentration-dependent inhibitory effect on the promoter induced lipid peroxidation. A 50% inhibitory activity of lipid peroxidation was observed at a protein concentration of 50 micrograms/ml. Ca(2+)-ATPase of rat brain homogenate was protected to nearly 50% of the initial activity from the lipid peroxidant induced inactivation by this protein. This protection of Ca(2+)-ATPase activity was found to be associated with the prevention of loss of -SH groups.

LIM genes parcellate the embryonic amygdala and regulate its development

The mechanisms that regulate the development of the amygdaloid complex are as yet poorly understood. Here, we show that in the absence of the LIM-homeodomain (LIM-HD) gene Lhx2, a particular amygdaloid nucleus, the nucleus of the lateral olfactory tract (nLOT), is selectively disrupted. LIM family members are well suited for multiple roles in the development of complex structures because they participate in regulatory interactions that permit a diversity of function. To investigate the possible role for other LIM-HD genes as well as LIM-only (Lmo) genes in the developing amygdala, we examined their expression in the embryo. We show that amygdaloid nuclei upregulate distinct patterns of LIM gene expression from embryonic stages. This supports the hypothesis that LIM genes may participate in the mechanisms that control the development of the amygdala. The disruption of the nLOT in the Lhx2 mutant is the first evidence of a role for LIM-HD genes in the development of the amygdaloid complex. The combinatorial expression patterns of LIM genes suggest a comprehensive mechanism for patterning this structure.

Signals from the edges: the cortical hem and antihem in telencephalic development

The early cortical primordium develops from a sheet of neuroepithelium that is flanked by distinct signaling centers. Of these, the hem and the antihem are positioned as longitudinal stripes, running rostro-caudally along the medial and lateral faces, respectively, of each telencepahlic hemisphere. In this review we examine the similarities and differences in how these two signaling centers arise, their roles in patterning adjacent tissues, and the cells and structures they contribute to. Since both the hem and the antihem have been identified across many vertebrate phyla, they appear to be part of an evolutionary conserved set of mechanisms that play fundamental roles in forebrain development.

Effects of mutations in potential phosphorylation sites on transcytosis of FcRn

The neonatal Fc receptor, FcRn, transports immunoglobulin G (IgG) across intestinal epithelial cells of suckling rats and mice from the lumenal surface to the serosal surface. In cell culture models FcRn transports IgG bidirectionally, but there are differences in the mechanisms of transport in the two directions. We investigated the effects of mutations in the cytoplasmic domain of FcRn on apical to basolateral and basolateral to apical transport of Fc across rat inner medullary collecting duct (IMCD) cells. Basolateral to apical transport did not depend upon determinants in the cytoplasmic domain. In contrast, an essentially tailless FcRn was markedly impaired in apical to basolateral transport. Using truncation and substitution mutants, we identified serine-313 and serine-319 as phosphorylation sites in the cytoplasmic domain of FcRn expressed in Rat1 fibroblasts. Mutations at Ser-319 did not affect transcytosis across IMCD cells. FcRn-S313A was impaired in apical to basolateral transcytosis to the same extent as tailless FcRn, whereas FcRn-S313D transported at wild-type levels. FcRn-S313A recycled more Fc to the apical medium than the wild-type receptor, suggesting that Ser-313 is required to allow FcRn to be diverted from an apical recycling pathway to a transcytotic pathway.

Mechanisms underlying the specification, positional regulation, and function of the cortical hem

The cortical hem was first described as a potential signaling center at the telencephalic midline because of an enriched expression of multiple members of the Wnt and Bmp families of morphogens, and its position at the border between the presumptive cortex and the choroid plexus. There is now definitive evidence that the cortical hem is an organizing center in the telencephalon, and that it instructs the formation of the hippocampus. In this review, we present an analysis of the molecular and cellular events that lead to the formation of the cortical hem, and define its position and extent in the telencephalon. This directly controls the positioning of the hippocampus within the telencephalon. We conclude with a summary of the current understanding of the role of the hem as the hippocampal organizer.

Phage display selection can differentiate insecticidal activity of soybean cystatins

Plant cysteine proteinase inhibitors (phytocystatins) have been implicated as defensive molecules against Coleopteran and Hemipteran insect pests. Two soybean cystatins, soyacystatin N (scN) and soyacystatin L (scL), have 70% sequence identity but scN is a much more potent inhibitor of papain, vicilin peptidohydrolase and insect gut proteinases. When these cystatins were displayed on phage particles, papain-binding affinity and CPI activity of scN were substantially greater than those of scL, in direct correlation with their relative CPI activity as soluble recombinant proteins. Furthermore, scN substantially delayed cowpea weevil (Callosobruchus maculatus (F.)) growth and development in insect feeding bioassays, whereas scL was essentially inactive as an insecticide. Papain biopanning selection of phage-displayed soyacystatins resulted in a 200-1000-fold greater enrichment for scN relative to scL. These results establish that binding affinity of cystatins can be used in phage display biopanning procedures to select variants with greater insecticidal activity, illustrating the potential of phage display and biopanning selection for directed molecular evolution of biological activity of these plant defensive proteins.

Association of MMP7 -181A→G Promoter Polymorphism with Gastric Cancer Risk: INFLUENCE OF NICOTINE IN DIFFERENTIAL ALLELE-SPECIFIC TRANSCRIPTION VIA INCREASED PHOSPHORYLATION OF cAMP-RESPONSE ELEMENT-BINDING PROTEIN (CREB)

Elevated expression of matrix metalloproteinase7 (MMP7) has been demonstrated to play a pivotal role in cancer invasion. The -181A→G (rs11568818) polymorphism in the MMP7 promoter modulates gene expression and possibly affects cancer progression. Here, we evaluated the impact of -181A→G polymorphism on MMP7 promoter activity and its association with gastric cancer risk in eastern Indian case-control cohorts (n = 520). The GG genotype as compared with the AA genotype was predisposed (p = 0.02; odds ratio = 1.9, 95% confidence interval = 1.1-3.3) to gastric cancer risk. Stratification analysis showed that tobacco addiction enhanced gastric cancer risk in GG subjects when compared with AA subjects (p = 0.03, odds ratio = 2.46, and 95% confidence interval = 1.07-5.68). Meta-analysis revealed that tobacco enhanced the risk for cancer more markedly in AG and GG carriers. Activity and expression of MMP7 were significantly higher in GG than in AA carriers. In support, MMP7 promoter-reporter assays showed greater transcriptional activity toward A to G transition under basal/nicotine-induced/cAMP-response element-binding protein (CREB) overexpressed conditions in gastric adenocarcinoma cells. Moreover, nicotine (a major component of tobacco) treatment significantly up-regulated MMP7 expression due to enhanced CREB phosphorylation followed by its nuclear translocation in gastric adenocarcinoma cells. Furthermore, chromatin immunoprecipitation experiments revealed higher binding of phosphorylated CREB with the -181G than the -181A allele. Altogether, specific binding of phosphorylated CREB to the G allele-carrying promoter enhances MMP7 gene expression that is further augmented by nicotine due to increased CREB phosphorylation and thereby increases the risk for gastric cancer.

How mechanisms of stem cell polarity shape the human cerebral cortex

Apical-basal progenitor cell polarity establishes key features of the radial and laminar architecture of the developing human cortex. The unique diversity of cortical stem cell populations and an expansion of progenitor population size in the human cortex have been mirrored by an increase in the complexity of cellular processes that regulate stem cell morphology and behaviour, including their polarity. The study of human cells in primary tissue samples and human stem cell-derived model systems (such as cortical organoids) has provided insight into these processes, revealing that protein complexes regulate progenitor polarity by controlling cell membrane adherence within appropriate cortical niches and are themselves regulated by cytoskeletal proteins, signalling molecules and receptors, and cellular organelles. Studies exploring how cortical stem cell polarity is established and maintained are key for understanding the features of human brain development and have implications for neurological dysfunction.

Catestatin Gly364Ser Variant Alters Systemic Blood Pressure and the Risk for Hypertension in Human Populations via Endothelial Nitric Oxide Pathway

Catestatin (CST), an endogenous antihypertensive/antiadrenergic peptide, is a novel regulator of cardiovascular physiology. Here, we report case-control studies in 2 geographically/ethnically distinct Indian populations (n≈4000) that showed association of the naturally-occurring human CST-Gly364Ser variant with increased risk for hypertension (age-adjusted odds ratios: 1.483; P=0.009 and 2.951; P=0.005). Consistently, 364Ser allele carriers displayed elevated systolic (up to ≈8 mm Hg; P=0.004) and diastolic (up to ≈6 mm Hg; P=0.001) blood pressure. The variant allele was also found to be in linkage disequilibrium with other functional single-nucleotide polymorphisms in the CHGA promoter and nearby coding region. Functional characterization of the Gly364Ser variant was performed using cellular/molecular biological experiments (viz peptide-receptor binding assays, nitric oxide [NO], phosphorylated extracellular regulated kinase, and phosphorylated endothelial NO synthase estimations) and computational approaches (molecular dynamics simulations for structural analysis of wild-type [CST-WT] and variant [CST-364Ser] peptides and docking of peptide/ligand with β-adrenergic receptors [ADRB1/2]). CST-WT and CST-364Ser peptides differed profoundly in their secondary structures and showed differential interactions with ADRB2; although CST-WT displaced the ligand bound to ADRB2, CST-364Ser failed to do the same. Furthermore, CST-WT significantly inhibited ADRB2-stimulated extracellular regulated kinase activation, suggesting an antagonistic role towards ADRB2 unlike CST-364Ser. Consequently, CST-WT was more potent in NO production in human umbilical vein endothelial cells as compared with CST-364Ser. This NO-producing ability of CST-WT was abrogated by ADRB2 antagonist ICI 118551. In conclusion, CST-364Ser allele enhanced the risk for hypertension in human populations, possibly via diminished endothelial NO production because of altered interactions of CST-364Ser peptide with ADRB2 as compared with CST-WT.

Functional genetic variants of the catecholamine-release-inhibitory peptide catestatin in an Indian population: allele-specific effects on metabolic traits

Catestatin (CST), a chromogranin A (CHGA)-derived peptide, is a potent inhibitor of catecholamine release from adrenal chromaffin cells and postganglionic sympathetic axons. We re-sequenced the CST region of CHGA in an Indian population (n = 1010) and detected two amino acid substitution variants: G364S and G367V. Synthesized CST variant peptides (viz. CST-Ser-364 and CST-Val-367) were significantly less potent than the wild type peptide (CST-WT) to inhibit nicotine-stimulated catecholamine secretion from PC12 cells. Consistently, the rank-order of blockade of nicotinic acetylcholine receptor (nAChR)-stimulated inward current and intracellular Ca(2+) rise by these peptides in PC12 cells was: CST-WT > CST-Ser-364 > CST-Val-367. Structural analysis by CD spectroscopy coupled with molecular dynamics simulations revealed the following order of α-helical content: CST-WT > CST-Ser-364 > CST-Val-367; docking of CST peptides onto a major human nAChR subtype and molecular dynamics simulations also predicted the above rank order for their binding affinity with nAChR and the extent of occlusion of the receptor pore, providing a mechanistic basis for differential potencies. The G364S polymorphism was in strong linkage disequilibrium with several common CHGA genetic variations. Interestingly, the Ser-364 allele (detected in ∼15% subjects) was strongly associated with profound reduction (up to ∼2.1-fold) in plasma norepinephrine/epinephrine levels consistent with the diminished nAChR desensitization-blocking effect of CST-Ser-364 as compared with CST-WT. Additionally, the Ser-364 allele showed strong associations with elevated levels of plasma triglyceride and glucose levels. In conclusion, a common CHGA variant in an Indian population influences several biochemical parameters relevant to cardiovascular/metabolic disorders.

Clinical improvements following bilateral anterior capsulotomy in treatment-resistant depression

BACKGROUND

The purpose of this study was to evaluate a programme of lesion surgery carried out on patients with treatment-resistant depression (TRD).

METHOD

This was a retrospective study looking at clinical and psychometric data from 45 patients with TRD who had undergone bilateral stereotactic anterior capsulotomy surgery over a period of 15 years, with the approval of the Mental Health Act Commission (37 with unipolar depression and eight with bipolar disorder). The Beck Depression Inventory (BDI) before and after surgery was used as the primary outcome measure. The Montgomery-Asberg Depression Rating Scale was administered and cognitive aspects of executive and memory functions were also examined. We carried out a paired-samples t test on the outcome measures to determine any statistically significant change in the group as a consequence of surgery.

RESULTS

Patients improved on the clinical measure of depression after surgery by -21.20 points on the BDI with a 52% change. There were no significant cognitive changes post-surgery. Six patients were followed up in 2013 by phone interview and reported a generally positive experience. No major surgical complications occurred.

CONCLUSIONS

With the limitations of an uncontrolled, observational study, our data suggest that capsulotomy can be an effective treatment for otherwise TRD. Performance on neuropsychological tests did not deteriorate.

Expression pattern of Drosophila translin and behavioral analyses of the mutant

Translin is an evolutionarily conserved approximately 27-kDa protein that binds to specific DNA and RNA sequences and has diverse cellular functions. Here, we report the cloning and characterization of the translin orthologue from the fruit fly Drosophila melanogaster. Under protein-denaturing conditions, purified Drosophila translin exists as a mixture of dimers and monomers just like human translin. In contrast to human translin, the Drosophila translin dimers do not appear to be stabilized by disulfide interactions. Drosophila translin shows a ubiquitous cytoplasmic localization in early embryonal syncytial stage, with an enhanced staining in ventral neuroblasts at later stages (8-9), which are probably at metaphase. An elevated expression was seen in several other cell types, such as cells around the tracheal pits in the embryo and oenocytes in the third instar larva. RNA in situ hybridization showed an increased expression in the ventral midline cells of the larval brain, suggesting a neuronal expression, which was corroborated by protein immunostaining. In adult flies, Drosophila translin is localized in the brain neuronal cell bodies and in early spermatocytes. Interestingly, Drosophila translin mutants exhibit an impaired motor response which is sex specific. Taken together, the multiple cellular localizations, the high neuronal expression and the attendant locomotor defect of the Drosophila translin mutant suggest that Drosophila translin may have roles in neuronal development and behavior analogous to that of mouse translin.

Effects of situational demand upon social enjoyment and preference in schizotypy

The socioemotional functioning of schizophrenic and schizotypic individuals is marked by withdrawal, poor organization, and limited emotional displays. Such behavioral tendencies and lack of social enjoyment in schizotypy could be linked to the relative situational demands or role ambiguity inherent in specific social activities. To determine whether high-schizotypy individuals prefer more clearly role-defined social activities (e.g., visiting relatives) to more ambiguous, novel situations (e.g., going alone to a party), the authors gathered reports from 52 high-schizotypy and 60 low-schizotypy individuals on their enjoyment and frequency of engaging in social situations varying in relative situational demand. Parallel reports were obtained from knowledgeable others. Group x Situational Demand interactions revealed the hypothesized pattern of reduced frequency and enjoyment ratings for ambiguous or novel situations by the high-schizotypy participants in both self and others' reports. Groups were more comparable in their reported frequency and enjoyment of less ambiguous situations. Results suggest the importance of situational demands in the socioemotional experience and behavioral withdrawal in schizotypy.

Seizure evoked regulation of LIM-HD genes and co-factors in the postnatal and adult hippocampus

The LIM-homeodomain (LIM-HD) family of transcription factors is well known for its functions during several developmental processes including cell fate specification, cell migration and axon guidance, and its members play fundamental roles in hippocampal development. The hippocampus is a structure that displays striking activity dependent plasticity.  We examined whether LIM-HD genes and their co-factors are regulated during kainic acid induced seizure in the adult rat hippocampus as well as in early postnatal rats, when the hippocampal circuitry is not fully developed.  We report a distinct and field-specific regulation of LIM-HD genes Lhx1,Lhx2, and Lhx9, LIM-only gene Lmo4, and cofactor Clim1a in the adult hippocampus after seizure induction. In contrast none of these genes displayed altered levels upon induction of seizure in postnatal animals.  Our results provide evidence of temporal and spatial seizure mediated regulation of LIM-HD family members and suggest that LIM-HD gene function may be involved in activity dependent plasticity in the adult hippocampus

A Common Tag Nucleotide Variant in MMP7 Promoter Increases Risk for Hypertension via Enhanced Interactions With CREB (Cyclic AMP Response Element-Binding Protein) Transcription Factor

MMP (matrix metalloproteinase)-7-a potent extracellular matrix degrading enzyme-is emerging as a new regulator of cardiovascular diseases. However, potential contributions of MMP7 genetic variations to hypertension remain unknown. In this study, we probed for the association of a tag single-nucleotide polymorphism in the MMP7 promoter (-181A/G; rs11568818) with hypertension in an urban South Indian population (n=1501). The heterozygous AG genotype significantly increased risk for hypertension as compared with the wild-type AA genotype (odds ratio, 1.60 [95% CI, 1.25-2.06]; P=2.4×10^-4); AG genotype carriers also displayed significantly higher diastolic blood pressure and mean arterial pressure than wild-type AA individuals. The study was replicated in a North Indian population (n=949) (odds ratio, 1.52 [95% CI, 1.11-2.09]; P=0.01). Transient transfection experiments using MMP7 promoter-luciferase reporter constructs revealed that the variant -181G allele conferred greater promoter activity than the -181A allele. Computational prediction and structure-based conformational and molecular dynamics simulation studies suggested higher binding affinity for the CREB (cyclic AMP response element-binding protein) to the -181G promoter. In corroboration, overexpression/downregulation of CREB and chromatin immunoprecipitation experiments provided convincing evidence for stronger binding of CREB with the -181G promoter. The -181G promoter also displayed enhanced responses to hypoxia and epinephrine treatment. The higher promoter activity of -181G allele translated to increased MMP7 protein level, and MMP7-181AG heterozygous individuals displayed elevated plasma MMP7 levels, which positively correlated with blood pressure. In conclusion, the MMP7 A-181G promoter polymorphism increased MMP7 expression under pathophysiological conditions (hypoxic stress and catecholamine excess) via increased interactions with CREB and enhanced the risk for hypertension in its carriers.

Functional Gly297Ser Variant of the Physiological Dysglycemic Peptide Pancreastatin Is a Novel Risk Factor for Cardiometabolic Disorders

Pancreastatin (PST), a chromogranin A-derived potent physiological dysglycemic peptide, regulates glucose/insulin homeostasis. We have identified a nonsynonymous functional PST variant (p.Gly297Ser; rs9658664) that occurs in a large section of human populations. Association analysis of this single nucleotide polymorphism with cardiovascular/metabolic disease states in Indian populations (n = 4,300 subjects) displays elevated plasma glucose, glycosylated hemoglobin, diastolic blood pressure, and catecholamines in Gly/Ser subjects as compared with wild-type individuals (Gly/Gly). Consistently, the 297Ser allele confers an increased risk (∼1.3-1.6-fold) for type 2 diabetes/hypertension/coronary artery disease/metabolic syndrome. In corroboration, the variant peptide (PST-297S) displays gain-of-potency in several cellular events relevant for cardiometabolic disorders (e.g., increased expression of gluconeogenic genes, increased catecholamine secretion, and greater inhibition of insulin-stimulated glucose uptake) than the wild-type peptide. Computational docking analysis and molecular dynamics simulations show higher affinity binding of PST-297S peptide with glucose-regulated protein 78 (GRP78) and insulin receptor than the wild-type peptide, providing a mechanistic basis for the enhanced activity of the variant peptide. In vitro binding assays validate these in silico predictions of PST peptides binding to GRP78 and insulin receptor. In conclusion, the PST 297Ser allele influences cardiovascular/metabolic phenotypes and emerges as a novel risk factor for type 2 diabetes/hypertension/coronary artery disease in human populations.

Functional promoter polymorphisms direct the expression of cystathionine gamma-lyase gene in mouse models of essential hypertension

Despite the well-known role of cystathionine γ-lyase (Cth) in cardiovascular pathophysiology, transcriptional regulation of Cth remains incompletely understood. Sequencing of the Cth promoter region in mouse models of genetic/essential hypertension (viz. Blood Pressure High [BPH], Blood Pressure Low [BPL] and Blood Pressure Normal [BPN] mice) identified several genetic variations. Transient transfections of BPH/BPL-Cth promoter-reporter plasmids into various cell types revealed higher promoter activity of BPL-Cth than that of BPH-Cth. Corroboratively, endogenous Cth mRNA levels in kidney and liver tissues were also elevated in BPL mice. Computational analysis of the polymorphic Cth promoter region predicted differential binding affinity of c-Rel, HOXA3 and IRF1 with BPL/BPH-Cth promoter domains. Over-expression of c-Rel/HOXA3/IRF1 modulated BPL/BPH-Cth promoter activities in a consistent manner. Gel shift assays using BPH/BPL-Cth-promoter oligonucleotides with/without binding sites for c-Rel/HOXA3/IRF1 displayed formation of specific complexes with c-Rel/HOXA3/IRF1; addition of antibodies to reaction mixtures resulted in supershifts/inhibition of Cth promoter-transcription factor complexes. Furthermore, chromatin immunoprecipitation (ChIP) assays proved differential binding of c-Rel, HOXA3 and IRF1 with the polymorphic promoter region of BPL/BPH-Cth. Tumor necrosis factor-α (TNF-α) reduced the activities of BPL/BPH-Cth promoters to different extents that were further declined by ectopic expression of IRF1; on the other hand, siRNA-mediated down-regulation of IRF1 rescued the TNF-α-mediated suppression of the BPL/BPH-Cth promoter activities. In corroboration, ChIP analysis revealed enhanced binding of IRF1 with BPH/BPL-Cth promoter following TNF-α treatment. BPL/BPH-Cth promoter activity was diminished upon exposure of hepatocytes and cardiomyoblasts to ischemia-like pathological condition due to reduced binding of c-Rel with BPL/BPH-Cth-promoter. Taken together, this study reveals the molecular basis for the differential expression of Cth in mouse models of essential hypertension under basal and pathophysiological conditions.

A haplotype variant of the human chromogranin A gene (CHGA) promoter increases CHGA expression and the risk for cardiometabolic disorders

The acidic glycoprotein chromogranin A (CHGA) is co-stored/co-secreted with catecholamines and crucial for secretory vesicle biogenesis in neuronal/neuroendocrine cells. CHGA is dysregulated in several cardiovascular diseases, but the underlying mechanisms are not well established. Here, we sought to identify common polymorphisms in the CHGA promoter and to explore the mechanistic basis of their plausible contribution to regulating CHGA protein levels in circulation. Resequencing of the CHGA promoter in an Indian population (n = 769) yielded nine single-nucleotide polymorphisms (SNPs): G-1106A, A-1018T, T-1014C, T-988G, G-513A, G-462A, T-415C, C-89A, and C-57T. Linkage disequilibrium (LD) analysis indicated strong LD among SNPs at the -1014, -988, -462, and -89 bp positions and between the -1018 and -57 bp positions. Haplotype analysis predicted five major promoter haplotypes that displayed differential promoter activities in neuronal cells; specifically, haplotype 2 (containing variant T alleles at -1018 and -57 bp) exhibited the highest promoter activity. Systematic computational and experimental analyses revealed that transcription factor c-Rel has a role in activating the CHGA promoter haplotype 2 under basal and pathophysiological conditions (viz. inflammation and hypoxia). Consistent with the higher in vitro CHGA promoter activity of haplotype 2, individuals carrying this haplotype had higher plasma CHGA levels, plasma glucose levels, diastolic blood pressure, and body mass index. In conclusion, these results suggest a functional role of the CHGA promoter haplotype 2 (occurring in a large proportion of the world population) in enhancing CHGA expression in haplotype 2 carriers who may be at higher risk for cardiovascular/metabolic disorders.